Original: Meanwhile, other companies developed their own applications (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.
Simplified: 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.