Personally if you ask me, I think GPL v3 rocks, You can still generate revenue from your work and providing source code is not likely to impact your profitability in a substantial way..
The conclusion I have come to is that VSTs are rampant targets of piracy, and I am still unsure how much profit stands to be gained by marketing tools in that saturated marketplace.. SO why not forgo all the extra work and licensing and just give the hackers what they want and charge a more affordable price for things so that people don't have a reason NOT to pay it..
If there were cool unique little instruments for $9.99 or so.. available with source code, then end users wouldn't immediately think "oh thats outside my hobbyist budget, lets search for a torrent", they could likely pay the cost and that would be more convenient than tracking down a hack, and the pirates wouldn't have anything to hack because there wouldn't be copy protection and the source code is right there.
I think the reality is most electronic musicians are hobbyists anyway, and they just want fun and novel new plugins to play with but can't afford hundreds of dollars for them because they don't make much (if any) profit from them anyway.
This is where I see iOS APPs being a great way to go and model to learn from, with AUv3 you can release plugins and there is virtually no piracy because the ios store is integrated, and the pricing model is more reasonable for hobbyists to obtain the apps.. hell yeah Ill pay up to 20 dollars sometimes for a cool new music toy, but usually more like 5, and with that kind of pricing theres no reason to look for hacks cause who has a computer but can't afford 5 dollars. At that pricing tier why would people even spend the extra effort hunting for a crack.
Just my thoughts. Unless you have some groundbreaking new idea for a proprietary DSP algorithm in which case you would be developing from scratch anyway and not likely to be reading this.. there isn't really any unique intellectual property to protect then and your only potential value in your work is in a unique combination of other peoples work, so then GPL v3 and opensource is a great route, and your value is in the conduit you provide to endusers, and in allowing other developers to "see what you did there".