GPL and a fuzzy line...

Here's a weird little question for all of you...

I have recently been promoted by the company I've been working for to be a full-time programmer. Previously, I had a few pet projects, but was mainly employed as a tech support rep.

Anyway, while not employed by the company in a programming capacity, and outside of company time, I created a PHP script to manage/verify form input. It uses an OOP approach, makes building user-input-based applications much easier, and I'm really proud of it.

I would like to release the script to whomever would want to use it (GPL, or whatever). I would also like to use it as part of applications that I'm developing within the company now.

By my interpretation of the GPL, I could make a non-distributed modification to use at work (as an employee) that would be protected by a NDA, as long as the company never tried to distribute it. I could then continue development on the GPL version as an independant programmer.

First off, is that interpretation correct?

Second...if I modified a GPL script that someone else wrote, I could submit the modifications as reccommendations for future versions...if I made a modification/bug fix at work, and "suggested" it for the GPL version, would that be completely shaky ground? Or if I didn't make the modification at work, and just modified the GPL version, and then downloaded the new version for work...

I dunno...I'm trying not to get screwed here.

MPEDrummer