Where can I find iOS Enterprise Developer Program terms of use (license)?
Take a look at the iOS Developer Enterprise Program FAQ. The key points are:


No ability to distribute apps on the App Store.
Only allows you to distribute your apps to employees or members of your organization through Ad Hoc distribution.
The program is for companies/organizations to develop and distribute proprietary in-house apps to their employees.
If you want to develop for other company than yours, that other company should enroll in the program and add you to their development team.