They want as many corporations as possible to build on Eclipse to take the wind out of VS's sails. They are not interested in making money from Eclipse. They are interested in limiting the influence of Microsoft on their enterprise customers. So the license is a strategic tool.
Linux is kind of an accident in that regard. Linus chose a license long before the big corporations found that they had to support Linux after they had successfully crushed each others' Unix business in a decade long war of attrition.
So Linux is GPL, but fortunately they found a way to interpret GPL in a way that didn't preclude closed source software on top of it. It's all in their definition of "linking".
Where this ingenious trick doesn't work, in the device drivers space, the whole thing breaks down, which every Linux on Laptop user has been able to experience for many many years. A single non-cooperative device manufacturer can prevent sleep and resume, power management and many other functions to not work properly for many users. So Linux has become almost exclusively a server platform, contrary to Linus Torvalds personal desires, but in agreement with the BigCorp strategy.
Just one question: Is dual licensing a common pattern or many other licenses are used frequently (BSD, CC)? Just wondering if there is such a protective and still free, clear licensing why people are not using it as a de facto standard?