I honestly don't know much about GPL and such. I've asked asherkin about this and answered basically "na, lgpl would still require plugins to be under a compatible license. I also doubt the metamod license could ever change after all these years. Not like it required copyright assignment for contributions".
If metamod was part of AlliedMods project, an exception could have been granted. But he also answered me: "that said, we wouldn't - if it can't survive the source code being publicly available, it's not going to survive a cheat developer getting their hands on a binary. Decompilation is trivial". While it's a motherfucker answer, you can't deny he's right too.

Anyway, this looks like there is no immediate solution unfortunately. That's said I'm always open to suggestions.

Ah, you misunderstand me. I don't intend to steal code, but maybe stealing some of ideas. I know how to code, I'm not some random beginner who copy-paste code.
Anyway, I understand your concern, but I can't do nothing. Each board has his own rules, and just because I'm the official maintainer doesn't mean I can magically change the GPL licence.
Personally, I would be okay in such situation, the author sends the source code to someone of the staff, to check its content and compiling it.Then author could use that. Fair comprise. Not sure what are the thoughts of admins (asherkin, BAILOPAN, etc) on this.

I'm not sure what you're saying that to me, this is completely unrelated to thread nor what I've said above. And I have no idea what you're talking about.

You did a good job s1lent. There are some good ideas. I'm here because I've seen your round_control.inc and since I'm redoing my own plugins, I got curious to see what you have done and maybe stealing being inspirated by your work.
It makes me think also all things related to CGameRules members/virtual functions should be supported by AMXX, probably in Ham. I guess I will give a try.