There are 2 applicable licenses for the VSD software:
ESA Software Community License (ESCL) – Type 2 (similar to a “Weak Copyleft” Open Source license *)
This license regulates the access to all VSD software as well as the requirements for modifying the VSD source code. It basically mandates that if any modifications to the VSD software (i.e. source code) are distributed, they have to be distributed and licensed by the same license; however a number of exceptions apply, allowing certain types of Modifications to be distributed under different licensing terms. This is similar to the LGPL which is also “contagious” or propagating, albeit in a less stringent manner with respect to e.g. GPL. For details, see ESA Software Community License – Type 2 – v1.0
ESA Software Community License (ESCL) – Type 3 license (similar to a “no Copyleft” Open Source license *)
This license will typically apply to 3rd-party integrations to VSEE which only rely on the VSEE DataCore. In this case, the VSEE DataCore is licensed separately under the Type 3 license, which mandates that except for credits, acknowledgments and the reference to the original license, derived SW may follow any license incl. proprietary. This license is similar to, e.g. the BSD license. For details, see ESA Software Community License – Type 3 – v1.0
*) Please note that none of the abovementioned license types can be considered as “Open Source” (according to the OSI or FSF definitions) since they contain a territorial limitation, incompatible with the Open Source principles (see 1.13).