What is the legal risk in including OSS and can we avoid it?

Hi
You need to check the terms under which the OSS you're developing upon has been made available. Although it is freely available, there may be restrictions on use for commercial purposes which will be problematic for you if you are making a product to sell. I think you should tackle the first issue before you figure out what you want to do yourselves with regards to publication of the code i.e. check that you are not violating the licence terms to begin with.

I've noticed that companies like Palamida are advertising free webinars for start-ups about IP and the use of OSS. It may be worth looking into the resources they provide to educate yourself further on the issue.