What are some alternatives?
When comparing Transifex and OneSky, you can also consider the following products
Crowdin - Localize your product in a seamless way
POEditor - The translation and localization management platform that's easy to use *and* affordable!
Smartling - Website localization & translation
Text United - A new, chaos-free way to get translations for your business
Lokalise - Localization tool for software developers. Web-based collaborative multi-platform editor, API/CLI, numerous plugins, iOS and Android SDK.
Weblate - Weblate is a free web-based translation management system.