Foren / Craftwork / Server-side / how can i limit a plugin work for just 1 domain

You need some code encoder. 

Stealed from somewere in net (pretty old info, but it gives the direction for search): 

- Source Defender
- PHP Screw
- Zend Encoder
- PBC
- PHTML Encoder
- NIA Encoder
- microCode
- POBS

But it's not a all time solutions. All files can be decompiled with more or less time and knowledge.