[tor-dev] Can I modify obfs4 proxy code for my purpose?

Hi.

I have some questions about modifying codes.

1. I wanna build a password protected obfs4 proxy sever with my VPS. I don't need that much privacy in terms of MITM for this. I just wanna know if it is ok to build such server in Tor network.

2.I wanna overrides some Javascript API with add-on. but... I just tried this with latest Torbrowser. it seems like I can't overrides some API's. Because same add-on I made worked on normal Firefox browser.  I wanna avoid some fingerprint tracking recently discovered.  Is there any reason to block overrides by add-on? Or am I missing something? I wanna know which is best way to do this. add-on or Torbrowser itself.

Thanks.