What has to be noted in the case of license terms for own developments if distributed in combination with free software?

If Open Source software and proprietary own developments are contained in a product and own license terms shall be used for the proprietary developments, care must be taken to ensure that the own license terms are not in conflict with the Open Source license terms.
It is a common error that use restrictions are applied to the whole software, so that a contradiction arises to the freedom of use granted by the Open Source licenses. It is therefore recommended to expressly limit the application of the own license terms to the software components to which they apply. This may, for example, be carried out by using a clause like the following:
"The software contains components which are licensed as Open Source software. The components to which this relates and the respective license terms are enclosed with this license text. The licensee is granted a non-exclusive right of usefor the Open Source Software by the respective right holders used; the conditions stipulated by the respective valid license terms apply. The license terms of this license only apply to the components which are not listed as Open Source software."
With respect to liability and warranty it may be clarified that there is a differentiation between the liability of the licensors of the Open Source components and the liability of the person or entity who is distributing the product:
"In relation to the licensor the regulations on liability and warranty in these license terms apply for the whole software. The liability and warranty regulations of the Open Source licenses only apply in relation to the respective right holders."