Is..

  Source license compatible with your license?  
   

Are you a lawyer?

No.

Is this legal advice?

No.

I've been sued for violating a license agreement based on your advice. Will you help me?

No, but I bought popcorn. Give me your case number.

Do licenses matter if I dynamically link?

The FSF says yes, but the jury is out. Probably.

I've modified a file with license X. What license(s) are my modifications under?

There has never been a legal case arguing that different portions of a source file are under different licenses. So unless the source file is public domain, your modifications are probably also under the license of the original file. You may have to state your modifications and distribute the file upon request, depending on the license's requirements.

Can I modify a file's copyright/licence notice?

No.

Can I create my own license, or modify a different license?

Usually, as long as you don't violate any trademarks of the original license authors. But you probably shouldn't, licenses are often vary particular.

2 or 3 Clause BSD, MIT, or ISC?

They are all functionally equivalent. If you're modifying a project using one of these licenses, you should just keep it. If you're writing new software, the ISC license is the shortest. However, if you want to make your ownership of any trademarks your software uses very clear, use 3-Clause BSD.

I found a bug

That's not a question. Please submit it here github.com/imtira/lc