My 2 cents
What I think: It should be allowed, you once (or somebody did) purchased a game from Enterbrain.
What you could do: You could use them and just go for it. These text pad agreements aside, Enterbrain would have to sell a hard case that you can use it only in an enterbrain product but not that one, or outside that one, but other stuff you can, just not that stuff. Pretty tough case that will probably get thrown out the second EB files.
What you should do: Just wait for Degica to re-release it, pay for it (again) and they will give you the magical fairy dust notepad that says now you can use it in [insert engine here] for now.
Ether way that grumpy sister up there works for Degica and by proxy is a representative for them so you have your answer.