WHMCS - WHMCS is an all-in-one client management, billing & support system for online businesses.
Crowdin - Localize your product in a seamless way
HostBill - HostBill is a powerful and flexible, all-in-one automation, billing, client management and support platform for online businesses.
POEditor - The translation and localization management platform that's easy to use *and* affordable!
Blesta - Blesta is professional client management, billing, and support software.
Lokalise - Localization tool for software developers. Web-based collaborative multi-platform editor, API/CLI, numerous plugins, iOS and Android SDK.