The "unauthorised" sale of Custom Catches (CCs) has been the source of so much controversy within the 7Seas Community. For the benefit of the doubt, others (especially the new fishers) may have been clueless about courtesy/protocol on how virtual novelties are to be distributed and circulated in Second Life. There were some instances where Custom Catches were deliberately being sold without prior consent from its creators, upsetting the latter. To make matters worse, others have even listed them up for sale in trading sites such as XStreetSL.com and even in popular auction sites like eBay.
Guard It As If Your Life Depended On It
Creators would spend a lot of man-hours in the conceptualisation and "building" of Custom Catches. Just trying to come up with a brilliant idea can be brain draining, especially if the inspiration and the motivation isn't there. We must try to understand how the creative-process behind a Custom Catch works. I'm definitely sure they don't appear with just a click of the mouse, albeit not even overnight. A lot of hard work, tired-sleepy eyes and headaches would be part of an investment that builders would have to focus onto a single custom.

What Do CC Builders Get Out Of It?
... they must be getting a lot?!...
You would be surprised... (if I am not mistaken) about 4L$ for every standard bait bucket. That is IF you do ever purchase your bait or gear at their vendors. So basically, they do get a small commission not for being Custom Catch builders but for simply having a 7Seas gear-vendor set-up at their fishing spot.
Why do they build customs then?
It's probably just being creative as an artists, not to mention the joy of creating stuff (... and I'm not only talking about Jen Shikami or Meissa Thorn here /me winks) . Perhaps seeing fishers and collectors very pleased with their work is what drives them to carry-on building for more. For whatever reason, there is surely an act of selflessness and thoughtfulness in every creation they make in their CPGS (Custom Prize Giver Servers).
The only way for a return of investment.
Some creators have put up their own personal vendors for those who wish to purchase their creations without having to fish customs out of a server (those that are not patient enough to wait for a specific CC catch). It's probably one of the few ways they can generate some income (about 75-300L$ per item) for their hard work to which, in my opinion isn't that much: About a fraction of what we actually spend on virtual clothes and accessories or the equivalent of a bulk-bait in some cases.

Why Am I Not Allowed To Re-Sell...
... paid for the bait and fished it myself, isn't the catch considered mine?...
While it is true that anything we catch is ours, there may be some limit to what we can actually do with them, apart from wearing as ornamental pets. Majority of the catches being offered are no-copy/no-modify/free-transfer giving us the option to offer them as gifts or for the really hard-to-get ones (SuperUltraRare in particular), trade them with fellow 7Seas collectors for an equivalent item in rarity...
Trading and giving them away is just about what we can do with the items we catch. Selling them however has its conditions and limitations. While some creators do specify that the unauthorised sale of their creations are prohibited, other builders do offer their personalised vendors with a percentage of the profit going out as a commission to a patron.
A few established creator-owned vendors are quite popular in the 7Seas Community; creations by Migizi North (pirate ships and unique CCs) and Amara Twilight (animated mermaid variations) can be found in other fishing areas apart from their own. While Custom Catches from Nya Raymaker (Grumbles the cat and "Neptune's Orchestra"), R&L Wharf (Snoopy variants), Sugar Rush (crabcakes, fed jellyfish, teacups etc) and Celeste Cazenove among the many others, offer their creations from vendors located on-site.

Basically, the bait we use is officially for catching 7Seas fishes and stuff. Custom Catches are being offered FOR FREE as a plus/incentive to fishers patronising their fishing area. One may say they are gifts for habitués, others would see them as an attraction to keep the venue interesting enough for frequenters.
There may be a way to get a return-of-investment for all the baits you consume while fishing. You may simply exchange your CCs for bait to those who are willing to trade. I'm sure that is acceptable, going around the idea of customs being openly tradeable.
Why can't I sell what I catch?
Out of respect and courtesy, most especially if you are in direct competition with the CCs creator. It is worse when the sellers intentionally offer customs below the suggested retail price (SRP). "Give to Caesar what is for Caesar", as the saying goes. After all the builders and creators are the reason (apart from the latest official releases from 7Seas) why fishing has been exciting lately for enthusiasts and collectors like us.
Reselling without proper consent...
... helps kill the desire for the creators to produce more customs!
It may even start a trend for catches to be made as no transfer rendering them untradeable, eventually taking off the fun in the fishing. Trading in my opinion is one major factor why we have gained so many friends from fishing: think the desire to Interact.
Official 7Seas catches are admittedly exciting enough for us already... But try to imagine a virtual fishing world without these Custom Catch variants? I shudder at the thought of it, it's like having my cuppa without any sugar... horrible... bleaughhhhh ack!

For fishing venue owners who don't have time to make their own customs, CPGS can now be rented on a weekly, monthly or quarterly basis. The popular ones have proven to be very effective in attracting sim-traffic as well as luring die-hard fish mongers into sims. Pictured above from BlaksleeWorld Beach are rentable custom servers from Migizi North, Alice Xue and Amara Twilight (please IM them for particlulars), and I am sure there are others more!
I'm not violating any IPR rules, just re-selling.
True, not re-creating or copying the work is not a violation of any Intellectual Property Rights (IPR) policy.
Comparable to buying a music CD or a DVD movie: To which we may be able to convert music into digital format (mp3, aac etc) or movies into mp4 or mpeg (plus any other similar formats) provided we only use them for our personal portable devices (PSP, iPod, mobile phones, digital players etc).
We may have the option to "convert" media but NOT NECESSARILY the rights to distribute or re-sell for profit. Unless of course we have acquired the permission or consent from its copyright owners. The unlawful sale and distribution violates anti-piracy laws, and you surely wouldn't want record labels and distributing companies breathing behind your neck, would you? (laughter)
The same can be said for all virtual items in Second Life, and in this case the various Custom Catches offered FREELY to be caught in 7Seas Fishing enabled areas. Catching these customs gives us ownership for the virtual item BUT does not give ownership for the copyright of the item. We may be allowed to trade the items or give them away for as long as we do not profit through selling without the consent of the copyright owner.
No, you don't have to register your copyright to have a copyright.

How different is it from reselling a book I recently bought?
A very good topic which was discussed in 7Seas Social Chat. While the thought of that is very true, in comparison there may be a difference. Publishers have been paid for the books being sold in book shops. What we do with the book after purchase: give it away, resell it, burn it or make paper airplanes with it, wouldn't affect the profit of the publisher.
However, the unauthorise sale of someone else's creation in Second Life would always mean profit loss for any creator/builder/owner, which may have negative RL implications as mentioned in the article below.
PLEASE READ THIS: very interesting and relevant: http://arstechnica.com/gaming/news/2008/10/dutch-court-imposes-real-world-punishment-for-virtual-theft.ars

Disclaimer: Before anybody here violently reacts and report me to the SL Police for "piracy", and to the creators of the above mentioned customs for "theft", these vendor boxes are for illustration purposes only and are not actual vendors.
Seriously though, if you do want a copy for storing your precious customs, just IM me. As long as you don't USE the bloody boxes as click-able vendors. lololol
To make it simple:
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Buying a CC from one of the official vendors at retail price and resell it, assuming it's quid pro quo, meaning sell only the same quantities you have bought may be acceptable. Trading up your FREE catches or simply giving them away as gifts is commonly acceptable. Putting up a FREE Custom Catch/fish giver in your fishing area, property or shop is very much accepted..
Selling the Custom Catches of others in your vendors and/or shops "without proper or prior consent from the creator/builder" is unacceptable.

7Seas Fishing As A Community
Although the 7Seas creators guild wouldn't be as harsh and severe when talking about being protective of their work, respecting their creations and giving professional courtesy (with much consideration to the efforts they have poured into their customs) would avoid us all the unsolicited drama. With so much RL drama going on in our lives, why bring some more to Second Life? lololol
Just thinking of the keywords mentioned here:
Respect, professional courtesy, generosity, understanding, consideration, support, friendship... we could go on forever citing all the good virtues we can get out of the 7Seas Community, but the bottom line is 7Seas Fishing has become one big happy family to most of us if not all. Since its inception to Second Life almost a year ago, I am not surprised that it has evolved to be one of the most popular in-world games to date and why more and more people get hooked into it. It simply is FUN and I haven't started talking about the social chat yet, have I? hahaha To readers who havent tried 7Seas Fishing yet, oh boy you are missing a lot mate!

It's but normal for a family to have the occasional quarrels, squabbles and drama. A little hair pulling here and there and face scratching is normal (growling and snarling included...) I guess hahaha. But one thing is certain, 7Seas Fishing is one heck of a family that doesn't believe in contraception as we will grow bigger, better and brighter (and as I have observed in social chat, even more hornier hahaha JK) in the months to come! whoopie!