MetaTrader4 is licensed (to brokers) under fairly strict conditions and only limited changes are permitted under the agreement (such as the icon, server files, instruments, EA's and scripts, etc). The broker is not permitted to change any of the actual code (such as the EXE or DLL files), and any changes to these files is in breach of the license agreement.
There are a number of brokers who have modified the internal DLL files that install with MT4 in order to provide additional functionality. The only way that these brokers would have known details of the internal functionality of MT4 would have been to reverse engineer the DLL files in question, MetaQuotes have clearly seen this as a breach of the license agreement.
So, it appears that MetaQuotes are enforcing their license conditions by stopping brokers who replace executable code with their own custom versions.
This change will have no impact on FST or any other application that uses a DLL that is called from an EA or a Script.