Simplify the following text for a Grade 15 native English-speaking person.
Original: Meanwhile , other companies developed their own applications ( Yahoo , MSN , Excite , Ubique , IBM ) , each with its own proprietary protocol and client ; users therefore had to run multiple client applications if they wished to use more than one of these networks .
Simplified: Meanwhile , other companies developed their own software ; ( Excite , MSN , Ubique , and Yahoo ) , each with its own proprietary protocol and client ; users therefore had to run multiple client applications if they wished to use more than one of these networks .