Licenses: GPL with BSD

I am planning on building my next version of my project on Yii. The current version is great for what it does and can do but the base MVC is not as powerful as YIi and redoing the current code is probably more of an hassle that just porting / starting over with a better base.

Because I’m using Yii and several Yii based applications, extensions and what not I’m now starting to face issues that I’m not used to, licensing.

BSD is awesome in the fact that i can go commercial and reap the benefits of all your hardwork. And that is what is bothering me. I plan to release my next version as ipensource to continue in the spirit of things. The possiblilty of a community / commercial might happen in the future but is more of a wait and see based on what people want rather than based on making money. I have plans to monetarize on services rather than code.

So, essentially, I plan to stay opensource. Allowing anybody to download and do what they want.

Now the issue is:

If the backend is mostly based on BSD but the front end is on based on the GPL what kinds of issues do I face? Also, is that legal?

Really would appreciate any comments and help!