The Evangelical Free Church was formed on the principle that the Gospel is bigger than certain doctrinal distinctives. This isn't an easy philosophy to navigate, since one man's secondary can be another man's essential.
On one end of the spectrum, you can have a statement of faith that is so brief, loose, and undefined that it harbors all kinds of liberalism. I've seen that happen with the Intervarsity Christian Fellowship. On the other end of the spectrum you can have a statement of faith that is so dense and filled with detail that it generates endless fighting. I've seen that happen among doctrine-minded Presbyterians.
One area that the EFCA agreed to set somewhat to the side was Calvinism/Arminianism. In our early days, eternal security became a hot issue. Moody Bible Institute and Dallas Seminary taught it strongly, but there were many in the EFCA who either weren't sure where they stood on it, or thought it was possible for a Christian to completely apostasize.
The EFCA national leaders decided to set that to the side. There are definite drop-off limits to this kind of tolerance -- to some Arminians, we insist that justification is by faith alone, not faith plus a lifetime of faithfulness and Gospel good works. To some Calvinists, we insist that election doesn't narrow God's love down to only the elect, or nullify the mandate for world evangelism.
It's also true that individual preachers, and congregations, will probably have convictions about Calvinism/Arminianism. Some will call themselves Calvinists, some will call themselves Arminians. Some will call themselves "Calminians", some remain undecided, and a few are uninterested by the whole thing. It's likely that entire EFCA congregations will have an over-all "drift" in certain directions (this will be true about a lot of different subjects, I bet).
There are loud people who will claim that Calvinists are all fatalists who don't think that choices make a difference, or that Arminians are all closet humanists who believe in self-salvation. In almost all cases, these are false, distorted cartoon versions of the truth. I have found that people who talk like this barely understand the other side's teachings, or are parroting what some preacher somewhere told them.
Biblically-knowledgeable Calvinists and Arminians agree on all the Christian foundations. James Arminius taught the unbelievers are spiritually dead, and that all positive movement toward God is excited by God's unmerited grace. On that subject, Arminius was far more Scriptural than some Christian people today who call themselves "Arminian."
John Calvin in his commentary taught that Christ propitiated the sins of the world without exception (he also taught particular atonement elsewhere in his writings, so I think he was self-contradictory, but nevertheless his comments on 1st John 2:2 are well-known). John MacArthur, a strong Calvinist, wrote a book a few years back about God's love for the world, a book which was aimed against hyper-Calvinism.
If some militant Calvinist thinks the five points of Calvinism are the exact same thing as Christianity itself, then (a) they're wrong, and (b) they won't like or fit into an Evangelical Free Church. The same goes for militant, hard-line Arminianism. But, if we are solid on the fundamentals, and show each other grace, and pray for each other, we can model Christian unity.