Summary: Electrum, a popular lightweight Bitcoin wallet, is making a big change with their latest release, version 2.6. It’s not necessarily in the form of fancy new features or major performance upgrades; rather it is in the form of their licensing.
Open source software relies on special usage licensing — otherwise it would be trivially easy for someone to take the open source code and re-release it as proprietary software. There are many different open source licenses with varying levels of freedom, such as the popular Apache, GPL, Mozilla, and MIT Licenses. The MIT License is one of the most open licenses; it simply requires any redistribution or modifications to also be released under the MIT License.
Under the new license terms, developers will have much more freedom to incorporate parts of Electrum’s code into their own software, a major factor in the decision to make the change. Certain parts of the Electrum code that were not compatible with the MIT license were modified or removed altogether. Version 2.6 is not yet released, although the source code has been made available.