One of the very important things all MooTools developers realise about
Core and More, is that a very large amount of products they're used in
are older products that are in maintenance mode and should need to
keep working. All changes to Core and More are made with that in mind,
so all changes are as compatible as possible.
MooTools has historically used a not-very-semver approach to
versioning, and it's still not using semver right now, but it's a lot
more controlled than it was in the 1.3-and-before era.
The way you can look at it currently is:
When a major version number increases, we do our best to do two
things: 1. include a compatibility "workaround", so you can build a
version 1.n+1 which is still compatible (you will find this in the
builder), and 2. list the incompatible changes in a blog post. In
cases where 1 isn't possible, we make sure we do 2 even more
In general, because MooTools Core's API and functionality has
stabilised over a lot of years, the changes are mostly to stay in line
with native implementations of similar or the same functionality. In
most cases these are only minor changes, and upgrading is easy enough
so you can stop using the compatibility builds.
The current Core version is 1.5.1, which by definition has a
completely compatible API to 1.5.0. (More is 1.5.1 as well, and works
with any Core 1.5.x, for that reason.) The changes from 1.4.5 are on
the blog (http://mootools.net/blog/2014/05/19/mootools-1-5-is-here
the backward incompatible changes are the first few bullets in the
list you'll find there.
(TLDR:) From all this, you have probably already gathered the answer
to your question, but to answer it directly: recent changes may have
changed subtleties in the public API, but nothing has really changed
about how to use the functions or property names. Especially the
examples you mention are things we very much try to keep stable.
Anticipating a next question: the "generation" part of the version
number is quite useless right now, it's pretty much stuck at 1. Yes,
there's been talks about a 2.x version. Yes, a lot of things have been
tried (there's an inactive 2.0wip branch with ideas from 2012, there
was Prime for a bit, etc.) No, there is no concrete plan or roadmap
for 2.x. One thing is sure, though, if or when there is a 2.x,
versioning will turn semver from there on, and it'll just be
Kind regards (and best wishes for the new year),