based on totally different platform of both CMS, iFrame would be the only solution I can think of (besides of re-implementing the module in ASP.net).

I'm finishing up porting a site from Xoops to DNN.  I had some custom php scripts that I used that I didn't want to recreate.  Tried using the IFrame module and had problems with it (can't recall specifics without digging out my notes).  Instead, I used an HTML module and put an IFrame in the source html. For example,

<p><iframe height="600" frameborder="0" width="800" marginwidth="10" src="/FFG_Files/phpscripts/buyoptions.php"></iframe></p>

This works fine.  In my php script I reference a css file that has the same style colors, fonts, etc. as my skin.

Hope that helps,

Joan