Tax Question for U.S. Retiree

There seems to be lots of info on the internet on the subject.  I copied this: 

Double Taxation
Double tax treaties exist that may provide tax relief where a Belgian tax resident also pays income tax in another country.

Tax Treatment of Expatriates Assigned to Belgium
Expatriates may qualify for a special tax regime. If expatriate status is granted by the tax authorities, the person is considered as a non-resident of Belgium for tax purposes.

In addition, an expatriate may receive the following allowances free of income tax, capped at €11,250 (managers) or exceptionally at €29,750 (scientists):

Cost of living (limited to €2,500)
Cost of housing
Tax equalisation
School fees (uncapped)
Since the qualifying expatriate is treated as a non-resident, his foreign-sourced income is not taxed in Belgium. Earned income connected to an activity that is carried out outside Belgium is therefore not taxed (this is the travel exclusion).