[donw]

In this case, though, you need to be careful if you decide that you want to turn around and sell your 'hacking' as a product. Because you used company resources (at-work time and equipment) to produce it, there is a strong legal precedent allowing your employer to claim ownership of your creation.

I'm in the position of working full-time and starting a company part-time, and am very careful to keep my two worlds separate, even though I'm 99.999% sure that my employer has no interest in attempting to take ownership the product I'm building.

[myelin]

Too true; be careful. You're probably safe using company time to learn (as mentioned in the parent^2), which the company might not actually mind if you put your skills to use for them as well, but if you use it to create your own product, you're on thin ice.