When an US citizen say liberal, he's talking about society. When an EU citizen say liberal, he's talking about economics. This make sometimes translation difficult.
In the context of the article, while US, with the focus on economics. They are using the classical or the european meaning.
But yeah Republican are conservatives on social policies and liberal on economics policies. Democrat are liberal on social policies and less liberal on economics (but still very liberal compared to an socialist party).
It includes a spectrum of different economic policies, such as freedom of movement, but it is always based on strong support for a market economy and private property in the means of production. Although economic liberalism can also be supportive of government regulation to a certain degree, it tends to oppose government intervention in the free market when it inhibits free trade and open competition.